Novel organosilicon compounds and a method for their production

ABSTRACT

Phosphorous-modified organosilicon compounds containing silicon-bound methoxy groups and a methylene spacer linking silicon to the phosphorous moiety are easily prepared in high yield and exhibit excellent hydrolysis rates. The compounds are useful, inter alia, as stabilizers in anti-freeze compositions, as cohydrolysis reactants in preparation of modified silicone resins, and in coatings.

The invention relates to novel phosphorus-modified organosiliconcompounds containing at least one methoxy group bound to the silicon anda process for preparing them by addition of silanes having ahalogen-carbon bond onto esters of phosphorous acid.

Phosphorus-modified alkylsilanes are of great economic interest in manyfields. They can be used, for example, as bonding agents, ascrosslinkers, for the functionalization of silicones, silicone resinssuch as silesquioxanes or metal oxides such as pyrogenic silicas or formodifying the properties of glycols.

The Japanese patent specification JP 63023976 describes a treatmentagent for solid materials which comprises an organopolysiloxane having aphosphonic ester group and improves the antistatic properties andhydrophobicity. Furthermore, the international published specificationWO 2002/055587 A1 likewise describes organopolysiloxanes containingphosphonic ester groups and also a process for preparing them for thefunctionalization of silicone resins such as silesquioxanes and theiruse as acid catalysts. In the patent specifications U.S. Pat. No.4,333,843, U.S. Pat. No. 4,367,154 and U.S. Pat. No. 4,676,919, theproperties, for example gelation resistance and storage stability orcorrosivity, of glycols is positively influenced by the addition oftrialkoxysilane propyl phosphonates.

Phosphorus-modified silanes have the sought-after ability ofsimultaneously improving the hydrophilicity, polarity, antistaticproperties, catalytic properties and the nonflammability of materialsmodified therewith.

Phosphorus-modified silanes are generally prepared by reaction oftrialkyl phosphites with chloropropyl-modified siloxanes or silanes, asdescribed, for example, in Gallagher et al., J. Polym. Sci. Part A, Vol.41, 48-59 (2003). A disadvantage of this reaction is that long reactiontimes and high temperatures are required, which leads to rearrangementsin the product and thus to losses in yield.

The reaction of trialkyl phosphites with chloromethyl-modified siloxanesas described in U.S. Pat. No. 2,768,193 or by Gallagher et al. proceedssignificantly more quickly, but has the disadvantage that the siloxanesprepared in this way can be purified by distillation only withdifficulty because of their high boiling point and, furthermore, aresuitable only to a limited extent for the functionalization of, forexample, silicone resins or as bonding agents, since the Si—O—Si bond onwhich they are based is virtually unreactive.

An alternative is the use of halomethyl-modified ethoxysilanes, which inthe reaction with trialkyl phosphites lead to distillablephosphonatoethoxysilanes. However, these ethoxysilanes have thedisadvantage that the chloromethylethoxysilanes used in the synthesisare not produced on an industrial scale and their hydrolysis rate isrelatively low. This leads to, for example, a cohydrolysis withmethoxysilanes to prepare functionalized silicone resins not being ableto be carried out, since the more reactive methoxysilanes reactcompletely first and the less reactive functional ethoxysilanes reactafterward.

A further possible way of preparing the desired compounds is thereaction of chloroalkylsilanes with phosphonates described in the patentspecification U.S. Pat. No. 3,019,248. However, this reaction is carriedout using metals, for example sodium, to increase the reaction rate,which is not readily able to be realized in industrial reaction plants.

It was then an object of the present invention to make it possible toobtain phosphorus-modified silanes which can be prepared in a verysimple fashion from commercially available chemicals in short reactiontimes and in good yields and at the same time have a high reactivity.

This object is achieved by phosphorus-modified silanes which contain atleast one methoxy group bound to the silicon and have the generalformula I:

where

-   the radicals R¹ are each, independently of one another, a    substituted or unsubstituted alkyl, alkenyl, cycloalkyl or aryl    group having from 1 to 18 carbon atoms or an alkoxy group having    from 2 to 18 carbon atoms,-   R² is a methoxy group,-   the radicals R⁴ are each, independently of one another, hydrogen, an    alkyl, cycloalkyl or aryl group which has from 1 to 18 carbon atoms    and may be substituted by fluorine, chlorine, alkoxy, amine, cyanate    or isocyanate groups or be unsubstituted,-   the radicals R⁵ are each, independently of one another, a    substituted or unsubstituted alkoxy group or aryloxy group having    from 1 to 18 carbon atoms, a substituted or unsubstituted    polyalkylene oxide having from 1 to 4000 carbon atoms and-   a is an integer from 0 to 2,    with the proviso that R¹, R⁴ or R⁵ can together be part of a cyclic    compound.

R¹ is preferably an alkyl radical and very particularly preferably amethyl radical. R⁴ is preferably hydrogen and R⁵ is preferably an alkoxygroup having 1-4 carbon atoms and very particularly preferably an ethoxygroup.

It has also been found that the desired target products can be obtainedin yields of greater than 75% when the products of the general formula Iare prepared by reacting compounds of the general formula II:X—(CR⁴ ₂)—Si—(R¹)_(a)(R²)_(3-a)  (II)where R¹, R², R⁴ are as defined above and X is fluorine, chlorine,bromine or iodine, with compounds of the general formula III:P(R⁵)₃  (III)where R₅ is as defined above.

X is a halogen, i.e. fluorine, chlorine, bromine or iodine, preferablychlorine or bromine, particularly preferably chlorine.

Here, an excess of preferably from 0.01 to 300 mol %, particularlypreferably from 10 to 100 mol %, of the reaction component of thegeneral formula III is reacted with a silane of the general formula IIat elevated temperature, preferably from 80 to 170° C., particularlypreferably from 100 to 155° C. This reaction can, if appropriate, becarried out in an inert solvent, but is preferably carried out withoutsolvent.

For example, the reaction components of the general formula III areplaced in a reaction vessel and the reaction component of the generalformula II is added while stirring. In another variant, the reactioncomponents of the general formula II are placed in a reaction vessel andthe reaction component of the general formula III is added whilestirring. The reaction time to be employed is generally from 10 to 1000minutes. The reaction is carried out at a temperature of from 0 to 300°C., preferably from 25 to 200° C., particularly preferably from 80 to170° C. The use of superatmospheric pressure, preferably up to 10 bar,may also be useful.

The crude products of the general formula I prepared in this way by theprocess of the invention are generally worked up by distillation, but ifthe reaction is carried out in an appropriate manner the work-up mayalso be able to be omitted.

The present invention further provides for the use of the inventivephosphorus-modified silanes of the general formula I as additives inantifreezes or as coating agent.

Furthermore, the cohydrolysis of the inventive phosphorus-modifiedsilanes of the general formula I in combination with alkoxyalkylsilanesfor preparing functionalized resins is also subject matter of thepresent invention.

The invention is illustrated by the following examples.

EXAMPLE 1

99.7 g (0.6 mol) of triethyl phosphite (P(OEt)₃, Aldrich, GC 98%) wereplaced under a nitrogen atmosphere in a 250 ml three-necked flaskprovided with a dropping funnel and reflux condenser. After heating to140° C., 46.4 g of chloromethyldimethoxymethylsilane (0.3 mol)(Wacker-Chemie GmbH) were slowly added dropwise over a period of 3 hourswhile stirring vigorously. The reaction mixture was subsequently heatedat 170° C. for another 30 minutes. After taking off the excess triethylphosphite under reduced pressure, 58.6 g ofdiethoxyphosphitomethyldimethoxymethylsilane (0.23 mol, GC 98%, yield:76% of theory) were distilled off at a temperature of 133° C. under apressure of 12 mbar.

EXAMPLE 2

46.4 g (0.3 mol) of chloromethyldimethoxymethylsilane (Wacker-ChemieGmbH) were placed under a nitrogen atomosphere in a 250 ml three-neckedflask provided with a dropping funnel and reflux condenser. Afterheating to 130° C., 75 g (0.45 mol) of triethyl phosphite (P(OEt)₃,Aldrich, GC 98%) were added dropwise with gas evolution (ethyl chloride)over a period of 3 hours while stirring vigorously. The reaction mixturewas subsequently heated at 170° C. for another 30 minutes. After takingoff the excess triethyl phosphite under reduced pressure, 65.1 g ofdiethoxyphosphitomethyldimethoxymethylsilane (255 mmol, GC 99%, yield:85% of theory) were distilled off at a temperature of 133° C. under apressure of 13 mbar.

EXAMPLE 3

124.5 g (0.75 mol) of triethyl phosphite (P(OEt)₃, Aldrich, GC 98%) wereplaced under a nitrogen atmosphere in a 250 ml three-necked flaskprovided with a dropping funnel and reflux condenser. After heating to140° C., 69.3 g of chloromethyldimethylmethoxysilane (0.5 mol)(Wacker-Chemie GmbH) were slowly added dropwise over a period of 2.5hours while stirring vigorously. The reaction mixture was subsequentlyheated at 170° C. for another 30 minutes. After taking off the excesstriethyl phosphite under reduced pressure, 100.4 g ofdiethoxyphosphitomethyldimethylmethoxysilane (0.42 mol, GC 98.2%, yield:83.6% of theory) were distilled off at a temperature of 118-122° C.under a pressure of 11 mbar.

EXAMPLE 4

12.2 g (0.675 mol) of triethyl phosphite (P(OEt)₃, Aldrich, GC 98%) wereplaced under a nitrogen atmosphere in a 250 ml three-necked flaskprovided with a dropping funnel and reflux condenser. After heating to140° C., 76.8 g of chloromethyltrimethoxysilane (0.45 mol)(Wacker-Chemie GmbH) were slowly added dropwise over a period of 2.5hours while stirring vigorously. The reaction mixture was subsequentlyheated at 170° C. for another 30 minutes. After taking off the excesstriethyl phosphite under reduced pressure, 105.6 g ofdiethoxyphosphitomethyltrimethoxysilane (0.39 mol, GC 97.4%, yield:86.2% of theory) were distilled off at a temperature of 135-138° C.under a pressure of 12 mbar.

EXAMPLE 5 Not According to the Invention

99.7 g (0.6 mol) of triethyl phosphite (P(OEt)₃, Aldrich, GC 98%) wereplaced under a nitrogen atmosphere in a 250 ml three-necked flaskprovided with a dropping funnel and reflux condenser. After heating to140° C., 85.1 g of chloromethyltriethoxysilane (0.4 mol) (Wacker-ChemieGmbH) were slowly added dropwise over a period of 1.5 hours whilestirring vigorously, The reaction mixture was subsequently heated at170° for another 1.5 hours to remove the ethyl chloride formed. Aftertaking off the excess triethyl phosphite under reduced pressure, 95.8 gof diethoxyphosphitomethyltrimethoxysilane (0.31 mol, GC 98%, yield:77.4% of theory) were distilled off at a temperature of 146° C. under apressure of 11-13 mbar.

EXAMPLE 6 Hydrolysis

The hydrolysis was carried out in aqueous solution at a pH of 4 whichwas set by means of sodium acetate/acetic acid buffer. The determinationof the conversion was carried out by means of NMR. The result is shownin Table 1. TABLE 1 Time Ethoxy groups on the Methoxy groups on the[min] triethoxysilane [mol %] trimethoxysilane [mol %] 0 100.00% 100.00%2 88.60% 33.30% 7 85.30% 12.30% 12 74.60% 4.80% 17 64.70% 2.00% 2255.90% 1.20% 27 48.50% 0.90% 32 41.50% 0.60% 37 36.30% 0.50% 42 31.00%n.d. 47 27.00% 0.50% 52 23.10% n.d. 57 20.00% n.d. 62 17.40% n.d. 1106.50% n.d.

The content of alkoxy groups bound to silicon was determined. It canclearly be seen that the methoxy derivatives according to the inventionhave a reaction rate which is from 15 to 20 times as high as that of theethoxy derivatives which are not according to the invention.

EXAMPLE 7

In a 250 ml flask, 13.5 g (50 mmol) ofdiethoxy-phosphitomethyltrimethoxysilane and 6 g ofdimethyldimethoxysilane were dissolved in 150 ml of a water/acetonesolution (50/50). The mixture was subsequently allowed to stand at roomtemperature for 3 days and the solvent mixture was subsequently removedon a rotary evaporator. This gave 14.1 g of a homogeneous white powderwhich was able to be identified by means of GPC and NMR as homogeneoussilicone resin without proportions of linear siloxane.

EXAMPLE 8

As a model for a commercial antifreeze, ethylene glycol was admixed withvarious corrosion inhibitors and additives. 917 g of ethylene glycol(Riedel-de Haen) were admixed with 13 g of sodium metaborate hydrate(Aldrich) (as 25% strength solution in ethylene glycol), 6 g of anaqueous sodium nitrate solution (33% by weight, Merck), a solution of 3g of sodium metasilicate Na₂SiO₃ (Aldrich) in 10 g of water, 1.5 ml of a10% strength NaOH solution and various contents ofdiethoxymethylphosphitotrimethoxysilane (referred to as silane). Themixture was subsequently heated to 80° C. and the temperature wasmaintained over a period of time. The time which elapsed until gelparticles occurred was measured. The corresponding gelation time isshown in Table 2. TABLE 2 Gelation time  0 ppm of silane  15 h  30 ppmof silane  70 h 100 ppm of silane 120 h 200 ppm 200 h

The example clearly shows that even small amounts of silane according tothe invention increase the stability of the antifreeze.

1-10. (canceled)
 11. A phosphorus-modified silane which contains atleast one methoxy group bound to the silicon and has the general formula(I):

where the radicals R¹ are each, independently of one another, asubstituted or unsubstituted alkyl, alkenyl, cycloalkyl or aryl grouphaving up to 18 carbon atoms or an alkoxy group having from 2 to 18carbon atoms, R² is a methoxy group, the radicals R⁴ are each,independently of one another, hydrogen, an alkyl, cycloalkyl or arylgroup which has up to 18 carbon atoms, optionally substituted byfluorine, chlorine, alkoxy, amine, cyanate or isocyanate group(s), theradicals R⁵ are each, independently of one another, a substituted orunsubstituted alkoxy group or aryloxy group having up to 18 carbonatoms, or a substituted or unsubstituted polyalkylene oxide having up to4000 carbon atoms and a is an integer from 0 to 2, with the proviso thattwo or more of R¹, R⁴ and R⁵ can together be part of a cyclic structure.12. A process for preparing phosphorus-modified silanes of claim 11which contain at least one methoxy group bound to silicon and have theformula (I):

where the radicals R¹ are each, independently of one another, asubstituted or unsubstituted alkyl, alkenyl, cycloalkyl or aryl grouphaving up to 18 carbon atoms or an alkoxy group having from 2 to 18carbon atoms, R² is a methoxy group, the radicals R⁴ are each,independently of one another, hydrogen, an alkyl, cycloalkyl or arylgroup which has up to 18 carbon atoms, optionally substituted byfluorine, chlorine, alkoxy, amine, cyanate or isocyanate group(s), theradicals R⁵ are each, independently of one another, a substituted orunsubstituted alkoxy group or aryloxy group having up to 18 carbonatoms, or a substituted or unsubstituted polyalkylene oxide having from1 to 4000 carbon atoms and a is an integer from 0 to 2, with the provisothat two or more of R¹, R⁴ and R⁵ can together be part of a cyclicstructure, wherein at least one compound of the formula (II):X—(CR⁴ ₂)—Si—(R¹)_(a)(R²)_(3-a)  (II) where X is fluorine, chlorine,bromine or iodine, is reacted with at least one compound of the formula(III):P(R⁵)₃  (III).
 13. The process of claim 12, wherein the reaction iscarried out at a temperature of from 0° C. to 300° C.
 14. The process ofclaim 12, wherein the reaction is carried out at a temperature of from80° C. to 170° C.
 15. The process of claim 12, wherein the reactioncomponent of the general formula III is reacted in an excess of from0.01 to 300 mol % with a silane of the formula (II).
 16. The process ofclaim 12, wherein the reaction component of the formula (III) is reactedin an excess of from 10 to 100 mol % with a silane of the formula (II).17. The process of claim 12, wherein the reaction is carried out in theabsence of a solvent.
 18. The process of claim 12, wherein the reactionis carried out at a pressure of from 1 to 10 bar.
 19. In an antifreezeor coating, the improvement comprising selecting as one component ofsaid antifreeze or coating, the phosphorus-modified silane of formula(I) of claim
 11. 20. A functionalized organopolysiloxane resin,comprising a cohydrolysis product of a phosphorous-modified silanes ofthe formula I of claim 11 in combination with at least onealkoxyalkylsilane.
 21. The phosphorous-modified silane of claim 11, incombination with one or more alkylene glycols comprising a stabilizedantifreeze.